1. Field of the Invention
The present invention relates generally to device testing, and in particular, relates to power continuity testing of devices performed in parallel.
2. Background Information
Power continuity testing is normally performed early in the test flow of integrated circuit devices to ensure that there are no undesirable short circuits in the devices"" power paths (e.g., a path from a Vcc or from a Vdd power supply to a component of the integrated circuit). Such power continuity testing is typically performed before proceeding with other tests, so that short circuits can be detected at the onset, thereby avoiding possible over-current damage to test hardware during the subsequent tests.
In a single-socket test system, power continuity testing can be a relatively simple task because a power supply can be programmed to perform the test easily on an individual device (sometimes referred to as a xe2x80x9cdevice under testxe2x80x9d or a xe2x80x9cDUTxe2x80x9d). For parallel testing, or in a parallel test system, power continuity testing often cannot simply test the current for all DUTs at once. This is because, if there is one DUT with a short circuit, all testing is stopped and all DUTs are removed from the parallel test system in order to examine or identify the faulty DUT. The testing may also need to be stopped because the DUT with the short circuit defect is drawing all of the current from the power supply and thus depriving the other DUTs of test current. These problems create a large penalty for each short-circuited DUT, especially when parallel testing is scaled to 20 or more DUTs.
To avoid this inefficiency, some parallel test systems provide a separate programmable power supply for each DUT, or provide a relay network that switches each DUT into connection with the power supply one at a time. These methods, in effect, turn the power continuity testing for the DUTs into a serial test(s) rather than a parallel test. Providing a separate power supply for each DUT is expensive, especially as the number of test sockets or DUTs requiring power continuity testing increases. Furthermore, such methods disadvantageously result in an increase in testing time and use lower-reliability circuits.